Diastereoselective atom transfer radical cyclization reactions of unsaturated α-bromo oxazolidinone imides catalyzed by Lewis acids
作者:Dan Yang、Bao-Fu Zheng、Shen Gu、Philip W.H. Chan、Nian-Yong Zhu
DOI:10.1016/j.tetasy.2003.06.001
日期:2003.10
A new Lewis acid-catalyzed atom transfer radical cyclization reaction of unsaturated α-bromo oxazolidinone imides is reported. In the presence of Lewis acids such as Mg(ClO4)2 and Yb(OTf)3, a series of trans cyclic products was obtained in high yield (up to 87%) between 0°C and room temperature. The loading of strong Lewis acids, such as Yb(OTf)3, can be reduced to 0.1 equiv. without significantly
报道了一种新的路易斯酸催化的不饱和α-溴恶唑烷二酮酰亚胺的原子转移自由基环化反应。在路易斯酸如Mg(ClO 4)2和Yb(OTf)3的存在下,可以在0℃至室温之间以高收率(高达87%)获得一系列反式环产物。强路易斯酸(例如Yb(OTf)3)的负载量可以降低到0.1当量。而不会显着降低产量。通过使用1,2-立体控制或手性恶唑烷酮助剂可以实现出色的非对映选择性。对于带有β-甲基取代基和手性助剂的底物1e和1f,(S)-(-)-4-苄基-5,5-二甲基-2-恶唑烷酮,产物的非对映异构体比率大于50:1。